Method of making a dispenser or a part thereof

ABSTRACT

A method for manufacturing a dispenser part, such as a dispenser or a part of a dispenser, having at least two component parts joined by a seam extending from a first side edge to a second side edge of the dispenser part. The method involves using a single mold and producing the dispenser part using a two component injection molding process. A dispenser or a dispenser part including at least two component parts joined by a seam achieved by the method, and a component part used in such a dispenser or dispenser part are also described.

TECHNICAL FIELD

The present invention concerns dispenser parts, in particular dispensersor parts of dispensers, comprising at least two components selected froma range of plastic materials, which components may be joined along aseam extending from a first side edge to a second side edge of thedispenser part. The invention also relates to a method for making suchdispenser parts.

BACKGROUND ART

In many types of dispensers it is for various reasons often desirable toprovide a dispenser part where at least an outer surface, a shell or asimilar dispenser part is made from two similar or different plasticmaterials. For instance, it is possible to make one section of thedispenser part transparent, in order to facilitate checking of the levelof a consumable product contained within the dispenser. A second sectioncan be made opaque in order to hide a dispensing mechanism, to allowmonitoring of the filling level and to provide a dispenser with anaesthetically pleasant appearance.

When making such a dispenser part, the first component is usuallyinjection moulded in a first mould and transferred to a second mould tobe joined by a subsequently injected component. A dispenser partmanufactured in this way may have problems with distortion of at leastthe first component, as well as of the seam, in particular in or nearthe regions of the side edges. The component parts are usually joinedend-to-end and even with local reinforcements, the seam may lacksufficient strength to withstand the forces it may be expected towithstand. For example, the front of the dispenser may be exposed toaccidental or intentional point loading, such as an impact force causedby an object or a person striking the dispenser. A weak seam may causethe dispenser part making up the cover to crack along at least part ofthe front surface, requiring the dispenser part to be replaced.

Various methods for manufacturing injection moulded products are knownfrom various prior art documents. WO 98/02361 relates to a knownovermoulding process, wherein a first component (a preform) is injectedinto a first mould. The preform is then transferred into a second mould,wherein a second material is injected and overmoulded onto the performto form a finished product, wherein the materials are joined along acontinuous, circular seam. Johannaber/Michaeli “Handbuch Sprizgiessen,6-Sonderverfahren der Spritzgiesstechnologie”, Carl Hanser Verlag,Munich, Del., is a handbook on injection moulding. Selected pages fromthis handbook relates to methods for overmoulding. JP 03-120022 shows aconventional overmoulding process, where two components are placed in amould and joined by injection moulding an additional material in a gapbetween the said components.

The object of the invention is to provide an improved dispenser part andmethod for making it, in order to solve the above problems relating tothe distortion of the dispenser part and the strength of the seam.

DISCLOSURE OF INVENTION

The above problems have been solved by a method for manufacturing adispenser part, such as a entire dispenser or a part of a dispenser, adispenser part and a component part made by this method according to theappended claims.

The invention relates to the manufacture of dispenser parts, inparticular dispensers or parts for dispensers for consumable materialsin restaurants, restrooms or similar. Dispensers of this type may beintended for rolls or stacks of paper or other wiping materials, or forwashing substances such as liquid hand cream, soap or other detergents.

In the subsequent text, terms such as front, rear, inner and outer aredefined in relation to a visible outer front or side surface of thedispenser itself or, where appropriate, a surface of a dispenser partlocated in a dispenser which surface faces the user. In addition, theterm “seam” is used as a general term defining any seam or jointsuitable for joining two component parts comprising plastic materialinto a single dispenser part. In general, the term “dispenser part” isused to denote both an entire dispenser as well as a structural part ofa dispenser. In the latter case, a structural part may comprise avisible outer cover, or a portion thereof, or a structural portion ofthe dispenser located inside an outer cover. Also, the term “componentpart” is used to denote each injection moulded component that is joinedwith one or more additional component parts to form a dispenser part.

According to a preferred embodiment, the invention relates to a methodof manufacturing a dispenser part comprising at least two componentparts each joined by a seam extending from a first side edge to a secondside edge of the dispenser part. When referring to a “dispenser part” inthe subsequent text, this term refers to a single part dispenser or toan internal part, an outer shell or an outer cover of a dispenser forpaper wipes/towels, coreless rolls, plastic or paper cups, liquidsoap/cream, or similar dispensers. The front part, shell or cover maycomprise two component parts made from the same or different plasticmaterials in any desired combination of opaque, semi-opaque,semi-transparent or transparent form. The component parts making up thedispenser part may also have functionally different properties, whereinthe component parts may comprise a cover section joined to a cuttingdevice using the method provided. However, the invention is not limitedto visible component parts, as a seam according to the invention mayalso be suitable for dispenser parts mounted internally in suchdispensers. The method involves using a single mould and producing thedispenser part using a two component injection moulding process.

The two component injection moulding process involves performing a firstinjection moulding step to produce at least a first part in said mould,retaining the at least one part in the mould, and performing a secondinjection moulding step to produce at least second part in said mouldand to complete the dispenser part. The mould is located in a firstposition during the first injection step, and is then moved or rotatedto a second position in which the second injection step and thesubsequent cooling is performed. In its simplest form, the method isused to make a dispenser part with a single first and second part. Sucha dispenser part may comprise an upper first part of a first material,being transparent, and a lower second part of a second material, beingopaque. However, a number of variations are possible within the scope ofthe invention. For instance, a dispenser part in the form of a frontcover may comprise a transparent first part, extending horizontallyacross a central portion of the dispenser part, and upper and loweropaque second parts, or vice versa. According to the invention, when thedispenser part comprises more than one first and one second part, allfirst parts are moulded in the first injection moulding step and allsecond parts are moulded in the second injection moulding step. Hencethe dispenser part may comprise at least one seam, where each componentpart is joined to an adjacent component part by a seam according to theinvention during the said injection moulding process.

A first edge of the at least one first part and an injected second edgeof the at least one second part are joined to form said seam during thesecond injection moulding step. Each first edge of the at least onefirst part is moulded to form at least one step in a transversedirection to the first edge. The at least one step is preferably, butnot necessarily, moulded along each first edge from the first to thesecond side edge of the first component part.

For each first part the at least one step may be moulded to form a firstcontact surface at right angles to an inner or an outer surface of thedispenser part, and a second contact surface extending towards the firstedge. Hence, the second contact surface is arranged to extend betweenthe inner and outer surfaces both in the transverse and the longitudinaldirection of the seam. The second contact surface may be moulded to formraised contact increasing means along the length of the seam, preferablyalong the entire length of the seam. The raised contact increasing meanswill melt upon contact with the material injected during the secondinjection moulding step.

In this context, the longitudinal direction of the seam is defined asthe direction of the front edge of the respective component part wherethey are joined by the seam, or the general direction of the front edgeshould the edge be non-linear. The transverse direction of the seam in aparticular location is defined as the direction at right angles to thesaid front edge in the plane of the dispenser part at the said location.

Each first edge of the first component part may be injection moulded toform at least two steps. This may be achieved by moulding the first edgeto form a third contact surface at right angles to an outer or an innersurface of the dispenser part. For instance, in its simplest form, theseam may comprise a first contact surface at right angles to an outersurface of the dispenser part, and a second contact surface extendingtowards the first edge. The seam is completed by a third contact surfaceat right angles to an inner surface of the dispenser part.

According to one example, the method involves moulding the raisedcontact increasing means to form at least one additional step in thesecond contact surface, between the first and third contact surfaces.The height of the steps may be selected depending on the thickness ofthe dispenser wall adjacent the seam and may for instance be selected ina range from 0.05 to 3 mm. The steps are preferably, but notnecessarily, given an equal height. For instance, in a seam connecting atransparent and an opaque part, the first step adjacent the outersurface of the dispenser part is preferably, but not necessarily, largerthan the additional steps. This gives a distinct line separating the twoparts and facilitates filling of the mould adjacent the edge of thefirst part during the second injection moulding step. An opaque materialhaving a thicker first step adjacent the seam will also prevent thisportion of the dispenser part from becoming partially transparent. Forinstance, a dispenser wall may have a constant total thickness of 1-6mm, preferably 2.5-4.5 mm, adjacent the seam. A first step providedadjacent the outer surface and a first step provided adjacent the innersurface may each have a height of 0.2-1 mm. These first and second stepsmay be separated by a number of intermediate additional steps with aheight of 0.05-1 mm. The intermediate steps are preferably, but notnecessarily of equal height. The separation between each adjacent stepmay be a distance equal to or greater than the height of the smaller ofsaid steps. Each corner of the said additional steps will melt duringthe second injection moulding step.

The steps may extend continuously or intermittently along the entirelongitudinal length of the seam. If the steps are arrangedintermittently, then the sum of all intermittent sections provided withsteps should have a total length not less than half the length of theseam. The spacing between adjacent stepped sections may be constant orvariable. Preferably, the stepped sections should coincide withnon-planar sections of the seam, such as corners, of sections that maybe subject to impact loading.

According to an alternative example, the method involves moulding thesaid raised contact increasing means to form at least one suitableprojection. Similar to the above example, each first edge of the firstcomponent part may be injection moulded to form at least two steps. Theseam may comprise a first contact surface at right angles to an outersurface of the dispenser part, and a second contact surface extendingtowards the first edge. The seam is completed by a third contact surfaceat right angles to an inner surface of the dispenser part. In thisexample, the height of the first and third contact surfaces may be equalto or approximately equal to half the thickness of the dispenser walladjacent the seam. The raised contact increasing means may form at leastone projection along the length of the seam, such as one or more flatprojections extending at right angles out of the second contact surfacealong the length of the seam.

Alternatively, the raised contact increasing means may form multiple,individual projections in at least one regular or irregular line alongthe length of the seam. The projections may also be evenly orintermittently distributed over the entire second contact surface,wherein a greater concentration of projections are provided alongportions of the seam subjected to relatively large forces during animpact. These projections may be shaped as circular, rectangular ortriangular columns, or as hemispherical, conical, pyramidal or V-shapedprojections. The projections may have a height up to approximately halfthe height of the first step, or the first contact surface. The largestcross-sectional dimension of a projection, measured at the base of sucha projection in the plane of the second contact surface, may be up totwice its height.

The projections may extend continuously or intermittently along theentire longitudinal length of the seam. If the projections are arrangedintermittently, then the sum of all intermittent sections provided withprojections should have a total length not less than half the length ofthe seam. The spacing between adjacent sections provided withprojections may be constant or variable. Preferably, the sectionsprovided with projections should coincide with non-planar sections ofthe seam, such as corners, of sections that may be subject to impactloading.

According to a further example, the method involves moulding the raisedcontact increasing means to form extended ridges. Similar to the abovealternative example, each first edge of the first component part may beinjection moulded to form at least two steps of equal height. In thisexample, the height of the first and third contact surfaces may be equalto or approximately equal to half the thickness of the dispenser walladjacent the seam. The raised contact increasing means may form at leastone ridge along the length of the seam. Such a ridge may have a V-shapedcross-section in the transverse direction of the seam. Alternatively,multiple, parallel ridges having a V-shaped cross-section may beprovided.

The ridges may extend continuously or intermittently along the entirelongitudinal length of the seam. If the ridges are arrangedintermittently, then the sum of all intermittent sections provided withridges should have a total length not less than half the length of theseam. The spacing between adjacent sections provided with ridges may beconstant or variable. Preferably, the sections provided with ridgesshould coincide with non-planar sections of the seam, such as corners,of sections that may be subject to impact loading.

In the above examples, the at least one projection or ridge may have aheight up to half the thickness of the first contact surface, measuredfrom the base of the projection to the outer surface of the finisheddispenser part in a direction at right angles to the said outer surface.The projections may be given the same or different heights.

The seam described in all the above examples may have a transverse widthextending over a distance of up to 5 times the thickness of the thinnerof the first and second parts, in a direction transverse to thedirection of the seam between the component parts in the plane of thesaid component parts.

If the first part comprises a transparent material, the steps are formedto reduce the thickness of each first edge towards the inner surface ofthe first part. The second part may comprise an opaque material and theopposing edge of the second part can be used to hide the raised contactincreasing means of the seam between the component parts. According toone example, the first and second parts may have the same thickness ateither side of and across the seam. According to a further example, thewall thickness of the first part may be gradually increased in thedirection of the edge of the first part adjacent the seam.

In order to achieve a desired strength each corner of the said steps, oreach projection, is arranged to melt during the second injectionmoulding step. It has been found that by providing steps formed bysubstantially right angled corners along the entire length of the seam,the formation of a homogenous, strong seam is achieved. When the moltenmaterial injected during the second injection moulding step reaches thesolidified edge of the first part, the corners or projections facilitatethe melting together of the first and second parts. In order to ensurethis, the temperature of the material to be injected and/or thetemperature or one or both mould may be controlled to achieve thedesired result. For instance, the temperature of the material injectedat least during the second injection moulding step may be selected abovethe recommended injection temperature for the particular material. Asthe second material flows through the mould towards the first part, itstemperature will gradually drop. However, as the initial temperature atthe start of the injection is higher than normal, the temperature of themolten second material will still be sufficient to melt the edge of thesolidified first part. The temperature of the first part may becontrolled by adjusting the cooling of the mould. The first part isretained in the mould after the first injection moulding step, in orderto maintain the shape of the first part as it begins to cool and tomaintain the first part at an elevated temperature until the secondinjection moulding step has been completed. The finished dispenser partmay then be cooled and removed from the mould.

In combination with a choice of compatible resin materials and suitableinjection temperatures for the first and second materials, a seam asdescribed above will have an improved impact strength as compared toprior art seams manufactured by conventional methods. The impactstrength can be defined as the energy required to fracture a specimensubjected to shock loading, as in an impact test. Alternative terms areimpact energy, impact value, impact resistance and energy absorption.

The invention further relates to a dispenser part manufactured by themethod as described above. The dispenser part comprises at least twoparts joined by a seam extending from a first side edge to a second sideedge of the dispenser part. The seam joining the respective first andsecond parts has an impact strength at least equal to that of either ofthe first and second parts adjacent the seam. In practice, this meansthat when subjected to an impact in the general area of the seam, thedispenser part will first fracture to one side of or parallel with theseam but not in or along the seam itself.

The invention also relates to a component part of a dispenser partmanufactured by the said method. The component part is an intermediateproduct arranged to be made during a first injection moulding step,wherein a first edge of the at least one first part comprises a numberof distinct steps. These steps have been described in the above text.

The dispenser part may comprise two or more injection moulded componentsjoined by a seam having a predetermined strength. This may be achievedby a dispenser part comprising a first injection moulded plasticcomponent part having an associated first mating surface; a secondinjection moulded plastic component part having an associated secondmating surface; and a seam formed by said first mating surface and saidsecond mating surface during injection moulding for joining said firstcomponent part and said second component part to define a dispenserpart. The strength of the resulting seam is preferably equal to orgreater than the strength of at least one of said first and secondmoulded plastic component parts. The impact strength of the resultingseam is preferably equal to or greater than the strength of at least oneof said first and second moulded plastic component parts.

The first mating surface and said second mating surface are generallynon-planar, in that the seam extends from a first side edge at a firstside wall of the dispenser part, across at least part of the frontsurface, and to a second side edge at a second side wall of thedispenser part.

In order to achieve the desired strength, the dispenser part should beinjection moulded using materials having suitable properties for thispurpose. According to one example, each of said first component and saidsecond component part is selected from the group acrylonitrile butadienestyrene (ABS) plastic material. According to a second example, the firstcomponent part is an ABS plastic material and said second component partis an methyl methacrylate-ABS (MABS) plastic material. Depending on thedesired properties or use of the dispenser part, the first componentpart may be an opaque ABS plastic material, and the second componentpart may be a transparent MABS plastic material. The transverse crosssectional thickness of the dispenser part at said seam may be between 1,and 6 mm, preferably between 2.5 and 4.5 mm.

As stated above, the first and second plastic component parts may bemoulded from the group selected from ABS plastic material. Alternativelya polycarbonate plastic material may be used, although such materialshave less scratch resistance. Similar to the ABS/MABS plastic materials,said polycarbonate plastic material may be either transparent or opaque.

The strength of the dispenser part across the seam should be such that,in bending, the seam has a peak load of at least 35 MPa, preferably over40 MPa, most preferably over 50 MPa. A comparison between a number ofseams according to the invention and a conventional seam will bedescribed in detail below. According to one example, a transverse crosssection of the seam may comprise at least one step or projection alongthe entire length of the seam, as described above.

The dispenser part may also comprise two or more injection mouldedcomponents joined by a continuous seam extending from one side of thedispenser part to another. This may be achieved by a dispenser partcomprising a first injection moulded plastic component part with anassociated first mating surface; a second injection moulded plasticcomponent part having an associated second mating surface; a seam formedby said first mating surface and said second mating surface duringinjection moulding for joining said first component part and said secondcomponent part to define a dispenser part, and component part comprisinga front surface, a first and a second side surface each having an edgefacing away from the front surface. The resulting seam is arranged toextend from the edge associated with the first side surface to the edgeassociated with the second side surface of the dispenser part. In thiscase, the first mating surface and the second mating surface aregenerally non-planar.

In order to achieve a non-planar seam connecting two components from afirst free edge to a second free edge, the dispenser part should beinjection moulded using materials having suitable properties for thispurpose. In addition to seam strength, it is desirable to use materialsthat do not shatter when subjected to an impact at or near the seam.

According to one example, each of said first component and said secondcomponent part is selected from the group acrylonitrile butadienestyrene (ABS) plastic material. According to a second example, the firstcomponent part is an ABS plastic material and said second component partis an methyl methacrylate-ABS (MABS) plastic material. Depending on thedesired properties or use of the dispenser part, the first componentpart may be an opaque ABS plastic material, and the second componentpart may be a transparent MABS plastic material. The transverse crosssection thickness of the dispenser part at said seam may be between 1,and 6 mm, preferably between 2.5 and 4.5 mm.

The seam should be able to withstand an impact of at least 10 joule, butpreferable 15 Joule without cracking at its free edges or alongnon-planar areas. A suitable method for testing seams according to theinvention, as well as conventional seams will be described in detailbelow. According to one example, a transverse cross section of the seammay comprise at least one step along the entire length of the seam.

The dispenser part may further comprise two or more injection mouldedcomponents joined by a seam shaped to provide a predetermined strengthand impact resistance. This may be achieved by a dispenser partcomprising at least one first injection moulded plastic component partwith an associated first mating surface; at least one second injectionmoulded plastic component part having an associated second matingsurface; a seam formed by said first mating surface and said secondmating surface during injection moulding for joining said firstcomponent part and said second component part to define a dispenserpart. A transverse cross section of the seam comprises a contact surfaceintermediate an inner and an outer surface of the dispenser part.

According to one example, the invention relates to a dispenser partcomprising at least two parts joined by a seam extending from a firstside edge, across a front surface and to a second side edge of thedispenser part. The dispenser part may comprise more than one first andsecond component part, each injected during a first and second injectionmoulding step, respectively. Hence, each first component part maycomprise one or two contact surfaces depending on the shape and/ordesign of the dispenser part.

Each contact surface is arranged to extend along the length of the seamand at least one contact surface may have a transverse extension of upto 5 times the thickness of at least one of the first or secondcomponent parts adjacent the seam. Alternatively, the contact surfacemay have a transverse extension between 3 and 5 times the thickness ofat least one of the first or second component parts adjacent the seam.The extent of the transverse extension of the contact surface may bedefined as the total length of the overlap between the first and secondcomponent parts at right angles to the seam parallel to the outersurface of the dispenser part. This at least one component is preferablythe thinner of the first and second component parts. Alternatively, itmay also be the component having a constant thickness leading up to theseam, in the transverse direction thereof. The seam may have a maximumthickness that is equal to or greater than that of at least one of thefirst or second component parts adjacent the seam. The maximum thicknessmay be 1.2 to 1.5 times the thickness of the said component parts.

Preferably, but not necessarily, the transverse cross section of theseam comprises a first step adjacent and at substantially right anglesto the outer surface of the dispenser part. The at least one stepextends along each first edge from the first to the second side edge.Each at least one step may form a first contact surface at right anglesto an inner or an outer surface of the dispenser part, and a secondcontact surface extending towards the first edge. The at least one stepis preferably moulded along each first edge from the first to the secondside edge of the first component part.

Hence, the second contact surface is arranged to extend between theinner and outer surfaces both in the transverse and the longitudinaldirection of the seam. The second contact surface may be moulded to formraised contact increasing means along the length of the seam, preferablyalong the entire length of the seam. The raised contact increasing meanswill melt upon contact with the material injected during the secondinjection moulding step.

Each first edge of the first component part may be injection moulded toform at least two steps. This may be achieved by moulding the first edgeto form a third contact surface at right angles to an outer or an innersurface of the dispenser part. For instance, in its simplest form, theseam may comprise a first contact surface at right angles to an outersurface of the dispenser part, and a second contact surface extendingtowards the first edge. The seam is completed by a third contact surfaceat right angles to an inner surface of the dispenser part.

According to one example, the method involves moulding the raisedcontact increasing means to form at least one additional step in thesecond contact surface, between the first and third contact surfaces.The height of the steps may be selected depending on the thickness ofthe dispenser wall adjacent the seam. This thickness is preferablymeasured at right angles to the front surface of the thinner of thecomponent parts immediately before the seam. The height of theadditional steps may for instance be selected in a range from 0.05 to 2mm. The steps are preferably, but not necessarily, given an equalheight. For instance, in a seam connecting a transparent and an opaquepart, the first step adjacent the outer surface of the dispenser part ispreferably, but not necessarily, larger than the additional steps. Thisgives a distinct line separating the two parts and facilitates fillingof the mould adjacent the edge of the first part during the secondinjection moulding step. An opaque material having a thicker first stepadjacent the seam will also prevent this portion of the dispenser partfrom becoming partially transparent. For instance, a dispenser wall ordispenser part may have a constant total thickness of 1-6 mm, preferably2.5-4.5 mm, adjacent the seam. A first step provided adjacent the outersurface and a first step provided adjacent the inner surface may eachhave a height of 0.2-1 mm. These first and second steps may be separatedby a number of intermediate additional steps with a height of 0.05-1 mm.The intermediate steps are preferably, but not necessarily of equalheight. The separation between each adjacent step may be a distanceequal to or greater than the height of the smaller of said steps. Eachcorner of the said additional steps will melt during the secondinjection moulding step.

According to an alternative example, the method involves moulding thesaid raised contact increasing means to form at least one suitableprojection. Similar to the above example, each first edge of the firstcomponent part may be injection moulded to form at least two steps. Theraised contact increasing means may form at least one projection alongthe length of the seam, such as one or more flat projections extendingat right angles to the second contact surface along the length of theseam.

Alternatively, the raised contact increasing means may form multiple,individual projections in at least one regular or irregular line alongthe length of the seam. The projections may also be evenly distributedover the entire second contact surface. These projections may be shapedas circular, rectangular or triangular columns, or as hemispherical,conical, pyramidal or V-shaped projections.

According to a further example, the method involves moulding the raisedcontact increasing means to form extended ridges. Similar to the aboveexample, each first edge of the first component part may be injectionmoulded to form at least two steps. The raised contact increasing meansmay form at least one ridge along the length of the seam. Such a ridgemay have a V-shaped cross-section in the transverse direction of theseam. Alternatively, multiple, parallel ridges having a V-shapedcross-section may be provided.

In the above examples, the at least one projection or ridge may have aheight up to half the thickness of the first contact surface, measuredfrom the base of the projection to the outer surface of the finisheddispenser part in a direction at right angles to the said outer surface.The projections may be given the same or different heights.

The seam described in all the above examples may have a transverse widthextending over a distance of up to 5 times the thickness of the thinnerof the first and second parts, in a direction transverse to thedirection of the seam between the component parts in the plane of thesaid component parts.

If the first part comprises a transparent material, the steps are formedto reduce the thickness of each first edge towards the inner surface ofthe first part. The second part may comprise an opaque material and theopposing edge of the second part can be used to hide the raised contactincreasing means of the seam between the component parts. According toone example, the first and second parts may have the same thickness ateither side of and across the seam. According to a further example, thewall thickness of the first part may be gradually increased in thedirection of the edge of the first part adjacent the seam.

According to a further example, the thickness of the first componentpart may be arranged to increase gradually in a transverse directiontowards the seam. The maximum thickness of the seam may be up to 1.5times the thickness of the second component part adjacent the seam. Aforward end of the first component part is arranged to extend past theseam in the transverse direction of said seam. Subsequently, the forwardend of the first component part may comprise a lip extending towards aninner surface of the second component part. In this way the total lengthof the contact surface as defined above, can be extended. This lip maybe suitably rounded or angled towards the said inner surface.

A dispenser part as described above may comprise a first and a secondcomponent part, each having a front surface, and a first and a secondside surface, each having an edge facing away from the common frontsurface. A seam according to the invention may be arranged to extendfrom the edge associated with the first side surface to the edgeassociated with the second side surface.

BRIEF DESCRIPTION OF DRAWINGS

The invention will be described in detail with reference to the attachedfigures. It is to be understood that the drawings are designed solelyfor the purpose of illustration and are not intended as a definition ofthe limits of the invention, for which reference should be made to theappended claims. It should be further understood that the drawings arenot necessarily drawn to scale and that, unless otherwise indicated,they are merely intended to schematically illustrate the structures andprocedures described herein.

FIGS. 1A-B show a schematic illustration of an arrangement for carryingout a moulding process for making a dispenser part according to theinvention;

FIG. 2 shows a schematic illustration of a dispenser part made by theprocess according to the invention;

FIG. 3 shows a schematic illustration of a prior art seam;

FIGS. 4A-D show a schematic illustration of cross-sections through anumber of alternative seams according to the invention;

FIG. 5 shows an enlarged view of the seam of FIG. 4A;

FIG. 6 shows a schematic enlarged section of a first dispenser partprovided with multiple steps according to a first example;

FIG. 7 shows a schematic enlarged section of a first dispenser partprovided with projections according to a second example;

FIG. 8 shows a schematic enlarged section of a first dispenser partprovided with a ridge according to a third example;

FIG. 9 shows a schematic enlarged section of a first dispenser partprovided with intermittent ridges according to a fourth example;

FIG. 10 shows a schematic illustration of a dispenser part provided withintermittent ridges as shown in FIG. 9;

FIG. 11 shows a schematic illustration of a dispenser part provided witha stepped edge as shown in FIG. 6;

FIG. 12A-C show illustrations of cross-sections through a number ofseams according to the invention;

FIG. 13 shows a first example of a dispenser comprising a dispenser partaccording to the invention;

FIG. 14 shows a second example of a dispenser comprising a dispenserpart according to the invention.

FIG. 15 shows a third example of a dispenser comprising a dispenser partaccording to the invention;

FIG. 16 shows a fourth example of a dispenser comprising a dispenserpart according to the invention;

EMBODIMENTS OF THE INVENTION

FIGS. 1A and 1B show a schematic illustration of an arrangement forcarrying out a two component injection moulding process for making adispenser part according to the invention.

In this example, the process uses two injection units 11, 12 and arotary mould M designed for sequential injection of a single part usingtwo different materials. In the subsequent text the process is describedfor the injection of a transparent and an opaque material, but it isapplicable for any combination of transparent and/or coloured materials.The mould M used in this example is a two cavity mould. The mould M isheld closed in a first cavity position shown in FIG. 1A and heated to apredetermined operating temperature. The first material, which isusually the material having the highest injection temperature, isinjected from the first injection unit 11 through a primary runnersystem 13 into a first cavity 15 to form a first component 17. In thisexample, the first material is a transparent or translucent resin.During the first injection, the mould volume to be occupied by thesecond material is shut off from the primary runner system. The mould isopened and a core plate is rotated 180°, as indicated by the arrow A,into a second cavity position shown in FIG. 1B, where after the mouldcloses. A secondary runner system 14 is connected to the volume to befilled and the second material is injected from the second injectionunit 12 into a second cavity 16 to form a second component 18. In thisexample, the second material is an opaque resin. After sufficientcooling of the injected dispenser part 17, 18, the mould is opened andthe dispenser part is ejected.

FIG. 2 shows a schematic illustration of a dispenser part 20 made by theabove process. The dispenser part 20 is made up of the two componentparts 17, 18 injected during the process shown in FIGS. 1A-B. The saidcomponent parts 17, 18 are joined along a seam 21, running from one sideedge 22 to a second side edge 23 of the dispenser part 20. FIG. 2further indicates the gating location 24 for the primary runner system13 and the corresponding gating location 25 for the secondary runnersystem 14.

One factor to consider during the process is the relative melttemperature of the two materials. As stated above the material havingthe highest injection temperature is usually injected first. In order toensure that the temperature of the second material is sufficient for atleast partially melting a cooperating edge of the first material, theinjection temperature of second material can be increased. The increasedtemperature can be higher than the injection temperature recommended bythe manufacturer, but not higher than the degradation temperature of thematerial.

In the above example, the first material was a transparent resin thatwas tested at two different injection temperatures. The second materialwas an opaque resin injected at the same temperature in both tests.These tests are described in further detail below.

Further factors are the mould wall temperature, the injection speed, thedelay time between injections, and the injected component parttemperature. For instance, the mould wall temperature is controlled tomaintain the first component part at a desired temperature duringrotation of the first component into the second injection position. Inthis way, the edge of the first component will not cause the injectedsecond material to cool before the cooperating edges have meltedtogether. The temperature of both components can also be maintainedduring the consecutive injections in order to minimize distortion of thedispenser part during the subsequent cooling of the complete dispenserpart. As each injection station is supplied by an independent injectionunit, injection speeds and pressures can be accurately controlled andadapted for each material being injected.

In addition to the tool design, additional considerations are the wallthickness of the injected component, the surface structure of the partfrom the primary runner system to avoid venting problems, the toolsurface and temperature for de-moulding, the gating location for optimumadhesion between component parts in dependence of flow path, and how thepart will be de-moulded, causing a force to be applied to the adhesionarea between component parts.

In order to increase adhesion between the contacting edges of the twomaterials the seam has been given a particular configuration. A priorart seam, as shown in FIG. 3, made by joining the same two materials wasused as a reference sample. The prior art sample was subjected to acomparative test using samples comprising a number of alternative seamsaccording to the invention and a sample comprising a length of ahomogenous opaque material having the same thickness as the referencesample. The seams according to the invention are shown in FIGS. 4A-4D.The test will be described in further detail below.

FIG. 3 shows a schematic illustration of a prior art seam between atransparent first component part 31 and an opaque second component part32. The first and second component parts 31, 32 have the same wallthickness and are joined end-to-end by a straight, flat seam 33.

FIGS. 4A-D show a schematic illustration of cross-sections through anumber of alternative seams according to the invention. FIG. 4A shows atransparent first component part 41 a and an opaque second componentpart 42 a. The first and the second component parts 41 a, 42 a have thesame wall thickness of 3 mm and are joined end-to-end by a seam 43 acomprising a number of steps. The seam extends over a distance 2.5 timesthe thickness of the second component part 42 a, in a directiontransverse to the direction of the seam 43 a between the componentparts. The front surfaces of the respective joined component parts arecompletely flush with each other along the seam. In the region of theseam, the leading edge of the second component part 42 a is arranged tooverlap the first component part 41 a in order to hide the seam 43 a.The seam 43 a will be described in further detail below (see FIG. 5). InFIGS. 4A-D the steps are shown as distinct steps with right angledcorners for clarity. However, in the finished seam between two injectionmoulded components, at least the corners of the contacting surfaces havemelted to form a fused seam. In order to achieve a desired strength eachcorner of the said steps is arranged to melt during the second injectionmoulding step. It has been found that by providing steps formed bysubstantially right angled corners along the entire length of the seam,the formation of a homogenous, strong seam is achieved. When the moltenmaterial injected during the second injection step reaches thesolidified edge of the first part, the corners facilitate the meltingtogether of the first and second parts. In order to ensure this, thetemperature of the material to be injected and/or the temperature of themould may be controlled to achieve the desired result.

FIG. 4B shows a transparent first component part 41 b and an opaquesecond component part 42 b. The first and second component parts 41 b,42 b are joined end-to-end by a seam 43 b comprising a number of steps.The seam extends over a distance 2.5 times the thickness of the secondcomponent part 42 b, in a direction transverse to the direction of theseam 43 b between the component parts. The first component part 41 b hasa wall thickness that is arranged to increase in the direction of thesecond component part 42 b. In order to avoid a visible increase of thetransparent first component 41 b, the wall thickness is increasedgradually from 3 mm to 4 mm over a distance of 65 mm from the front edgeof the first component 41 b. The increased wall thickness is located onthe inner, or rear, surface of the first component part 41 b. The secondcomponent part 42 b has a constant wall thickness of 3 mm. The frontsurfaces of the respective joined component parts are completely flushwith each other along the seam. In the region of the seam, a leadingedge of the first component part 41 b is provided with a lip 44 barranged to overlap the second component part 42 b in order to reinforceand hide the seam 43 b. The extent of the overlap in the transversedirection of the seam is up to the thickness of the dispenser part. Thethickness of the lip 44 b is gradually decreased to zero, for instanceby a rounded section shown in FIG. 4B. The part of the wall having anincreased thickness extends past the end of the stepped portion of theseam 43 b and is then rounded off towards the inner surface of thesecond component part 42 b.

FIG. 4C shows a transparent first component part 41 c and an opaquesecond component part 42 c. The first and second component parts 41 c,42 c are joined end-to-end by a seam 43 c comprising a number of steps.The seam extends over a distance 2.5 times the thickness of the secondcomponent part 42 c, in a direction transverse to the direction of theseam 43 c between the component parts. The first component part 41 c hasa wall thickness that is arranged to increase in the direction of thesecond component part 42 c. In order to reduce a visible increase of thetransparent first component 41 c, the wall thickness is increasedgradually in the said transverse direction. The wall thickness isincreased from 3 mm to 4 mm over a distance of 15 mm from the front edgeof the first component 41 c. The second component 42 c has a constantwall thickness of 3 mm. The front surfaces of the respective joinedcomponent parts are completely flush with each other along the seam. Inthe region of the seam, a leading edge of the first component part 41 cis provided with a lip 44 c arranged to overlap the second componentpart 42 c in order to reinforce and hide the seam 43 c. The extent ofthe overlap in the transverse direction of the seam is up to thethickness of the dispenser part. The thickness of the lip 44 c isgradually decreased to zero, for instance by a rounded section shown inFIG. 4C. The wall having an increased thickness extends past the end ofthe stepped portion of the seam 43 c and is then rounded off towards theinner surface of the second component part 42 c.

FIG. 4D shows a transparent first component part 41 d and an opaquesecond component part 42 d. The first and second component parts 41 d,42 d are joined end-to-end by a seam 43 d comprising a number of steps.The seam extends over a distance 2.5 times the thickness of the secondcomponent part 42 d, in a direction transverse to the direction of theseam 43 d between the component parts. The first component 41 d has awall thickness that is arranged to increase in the direction of thesecond component part 42 d. In order to avoid a visible increase of thetransparent first component 41 d, the wall thickness is increasedgradually and parallel to the angle of the seam in the said transversedirection. The wall thickness is increased from 3 mm to 4 mm from aposition on the inner surface immediately opposite the leading edge ofthe second component part 42 d where it contacts the first component 41d. The second component 42 d has a constant wall thickness of 3 mm. Thefront surfaces of the respective joined component parts are completelyflush with each other along the seam. In the region of the seam, aleading edge of the first component part 41 d is provided with a lip 44d arranged to overlap the second component part 42 d in order toreinforce and hide the seam 43 d. The extent of the overlap in thetransverse direction of the seam is up to the thickness of the dispenserpart. The thickness of the lip 44 d is gradually decreased to zero, forinstance by a rounded section shown in FIG. 4D. The part of the wallhaving an increased thickness extends parallel with and past the end ofthe stepped portion of the seam 43 d and is then rounded off towards theinner surface of the second component part 42 d.

FIGS. 4B-4D show a seam with an overlap, where an edge portion or a lip44 b, 44 c, 44 d on one dispenser part extends past the transverseextension of the seam. The lip 44 b, 44 c, 44 d partially overlaps therear surface on the opposite dispenser part to reinforce the seam.Comparative bending and impact tests have shown that an overlap of thistype will only give a limited improvement of the strength of the seam inbending. However, a noticeable positive effect was noted during impacttesting. Hence, in order to further improve the impact strength of adispenser part, an overlapping region as described above can be providedalong a portion of the seam that is likely to be subjected to an impact.An example of such a portion can be the front surface of an outer coverof a washroom paper towel dispenser.

FIG. 5 shows an enlarged view of the seam of FIG. 4A, comprising atransparent first component part 41 a and an opaque second componentpart 42 a. The front edge of the first component part 41 a is injectionmoulded to form a number of distinct steps 44, 45, 46. The height of thesteps is selected depending on the thickness of the dispenser walladjacent the seam 43 a. In this example, the dispenser wall thicknessadjacent the seam is 3 mm, and the height of the steps is selected basedon this measurement. For instance, in a seam 43 a connecting atransparent part 41 a and an opaque part 42 a, a first step 44 adjacentthe outer surface 47 of the dispenser part has been selected larger thana number of intermediate steps 45. This gives a distinct line separatingthe two parts 41 a, 42 a and facilitates filling of the mould adjacentthe edge of the first part 41 a during the second injection mouldingstep. A higher first step 46 adjacent the seam 43 a will also preventthis portion of the dispenser part from becoming partially transparent.Similarly, a final step 46 adjacent the inner surface 48 of thedispenser part has been selected larger than the intermediate steps 45to facilitate filling of the mould adjacent the edge of the first part41 a. In the latter case, the steps 44, 46 provided adjacent both theouter and the inner surfaces 47, 48 have each been given a height of 0.2mm. For a dispenser wall having a constant total thickness of 2 mm theseouter, first steps can be separated by a number of intermediate steps of0.05-0.1 mm. In this case the intermediate steps have an equal height of0.05 mm.

FIG. 6 shows a schematic enlarged section of a component part providedwith multiple steps as shown in according to a first example. Thiscomponent part corresponds to the first component part 41 a shown inFIG. 5. As described above, the front edge of the first component part41 a is injection moulded to form a number of distinct steps 44, 45, 46during a first injection moulding step according to the invention. Afirst step 44 adjacent the outer surface 47 of the component part has alarger height than a number of intermediate steps 45. Similarly, a finalstep 46 adjacent the inner surface 48 of the component part has beenselected larger than the intermediate steps 45 to facilitate filling ofthe mould adjacent the edge of the first component part 41 a. The firstcomponent part 41 a will be joined to the second component part 41 b(see FIG. 5) during the second injection moulding step.

FIG. 7 shows a schematic enlarged section of a first component part 51provided with projections 52 according to a second example. According tothis example, a contact surface 53 is provided with raised contactincreasing means in the form of a number of conical projections 52.Similar to the above example, the front edge of the first component part51 is injection moulded to form at least two steps 54, 56. A first step54 adjacent an outer surface 57 of the component part has a heightcorresponding to half the thickness of the first component part 51. InFIG. 7 the raised contact increasing means form two rows 55 a, 55 b ofconical projections 52 along the length of the front edge.Alternatively, the multiple, individual projections can be arranged inat least one regular or irregular line along the length of the seam. Theprojections can also be evenly distributed over the entire secondcontact surface. The front edge with its associated projections 52,contact surface 53 and steps 54, 56 will subsequently form part of aseam between the first component part 51 and an injection moulded secondcomponent part (not shown) to form a dispenser part.

FIG. 8 shows a schematic enlarged section of a first component part 61provided with a ridge 62 according to a third example. According to thisexample, a contact surface 63 is provided with raised contact increasingmeans in the form a ridge 62 extending parallel to a front edge of thefirst component part 61. Similar to the above example, the front edge ofthe first component part 61 is injection moulded to form at least twosteps 64, 66. A first step 64 adjacent an outer surface 67 of thecomponent part has a height corresponding to half the thickness of thefirst component part 61. In FIG. 8 the raised contact increasing meansform a single V-shaped ridge 62 along the length of the front edge.Alternatively the ridge may have an I- or U-shaped or a rectangularcross-section in the transverse direction of the front edge. Inaddition, multiple, parallel ridges can be provided. The front edge withits associated projections 62, contact surface 63 and steps 64, 66 willsubsequently form part of a seam between the first component part 61 andan injection moulded second component part (not shown) to form adispenser part.

FIG. 9 shows a schematic enlarged section of a first component part 71provided with intermittent ridges 72 a, 72 b according to a fourthexample. According to this example, a contact surface 73 is providedwith raised contact increasing means in the form of a flat, rectangular,or I-shaped ridge 72 a, 72 b extending parallel to a front edge of thefirst component part 71. Similar to the above example, the front edge ofthe first component part 71 is injection moulded to form at least twosteps 74, 76. A first step 74 adjacent an outer surface 77 of thecomponent part has a height corresponding to half the thickness of thefirst component part 51. In FIG. 9 the raised contact increasing meansform an intermittent I-shaped ridge 62, which ridge is provided forstrengthening selected portions along the length of the front edge.Alternatively the ridge may have an V- or U-shaped cross-section in thetransverse direction of the front edge. In addition, multiple, parallelridges can be provided, which intermittent ridges can be staggered. Thefront edge with its associated projections 72 a, 72 b, contact surface73 and steps 74, 76 will subsequently form part of a seam between thefirst component part 71 and an injection moulded second component part(not shown) to form a dispenser part.

In the above examples, as shown in FIGS. 6-9, the at least oneprojection or ridge may have a height up to half the thickness of thefirst step, measured from the base of the projection or ridge, in theplane of the first contact surface, to the outer surface of thedispenser part in a direction at right angles to the said outer surface.The projections/ridges can be given the same or different heights. Also,the resulting seam described in the above examples may extend over adistance of up to 5 times the thickness of the thinner of the first andsecond parts, in a direction transverse to the direction of the seambetween the component parts. For instance, in FIG. 6 the width of theresulting seam corresponds to the distance between first and secondsteps 44, 46 measured at right angles from the front edge.

FIG. 10 shows a schematic illustration of a component part 71 providedwith intermittent ridges 72 a, 72 b, 72 c, 72 d, 72 e as shown in FIG.9. As schematically indicated in FIG. 10, the ridges are located inareas where the strain caused by external loading is expected to berelatively large. For instance, a number of ridges 72 a, 72 b, 72 c arelocated closer together along a section A of a the middle of a frontsurface of the component part 71, which is likely to experience impactloading. The ridges 72 a, 72 b, 72 c can be placed closer togetherand/or be made longer in this section. An impact load on the frontsurface will also increase the strain in a corner section B of thecomponent part 71, requiring a reinforcing ridge 72 d in each suchsection B. The component part 71 also comprises a free side edge sectionC, which can be subjected to strain caused by both impact loading andforces induced in the material during cooling of the injection mouldeddispenser part. Hence each side edge section C is provided with areinforcing ridge 72 e. Note that the ridges in FIG. 10 are not drawn toscale, for reasons of clarity.

FIG. 11 shows a schematic illustration of the component part 41 aprovided with a stepped edge 80 comprising a number of distinct steps44, 45, 46, as shown in FIG. 6. In FIG. 11 it can be seen how thestepped edge 80 extends continuously from one side edge 81 of thecomponent part 41 a to a second side edge 82.

FIGS. 12A-12C show illustrations of actual photographs ofcross-sectional samples through a number of dispenser partscorresponding to the schematic cross-sections shown in FIGS. 4A-4C. InFIGS. 12A-12C the dispenser parts have been cut in a transversedirection of the seam between the first and second component parts.Hence FIG. 12A, corresponding to FIG. 4A, shows a transparent firstcomponent part 41 a and an opaque second component part 42 a. The firstand the second component parts 41 a, 42 a have the same wall thicknessof 3 mm and are joined end-to-end by a seam 43 a comprising a number ofsteps. As can be seen from the figure, the contact surfaces have beenjoined and the corners of the distinct steps have melted to form roundedsurfaces and merged with the second component part 42 a during thesecond injection moulding step.

FIGS. 12B and 12C show a transparent first component part 41 b, 41 c andan opaque second component part 42 b, 42 c. The first and secondcomponent parts 41 b, 42 b; 41 c, 42 c are joined end-to-end by a seam43 b, 43 c comprising a number of steps. The seam extends over adistance 2.5 times the thickness of the second component part 42 b, 42c, in a direction transverse to the direction of the seam 43 b, 43 cbetween the component parts. The first component part 41 b, 41 c has awall thickness that is arranged to increase in the direction of thesecond component part 42 b, 42 c. A leading edge of the first componentpart 41 b, 41 c is provided with a lip 44 b, 44 c arranged to overlapthe second component part 42 b, 42 c in order to reinforce and hide theseam 43 b, 43 c. As shown in FIG. 12A, the contact surfaces have beenjoined and the corners of the distinct steps have melted to form roundedsurfaces and merged with the second component part 42 b, 42 c during thesecond injection moulding step.

As opposed to a prior art solution as shown in FIG. 3, the seam betweentwo component parts is able to withstand an impact test subjecting thedispenser part to an impact of 15 joule. This test is described infurther detail below. When subjected to impact loading in excess of thatused in the said test, the dispenser part will crack adjacent andparallel to the seam.

FIG. 13 shows a first example of a dispenser comprising a dispenser partaccording to the invention. In this example, a dispenser part 90 isformed by a transparent first component part 91 and an opaque secondcomponent part 92. The first component part 91 and the second componentpart 92 are joined by a seam 93 extending from a first side edge 94 to asecond side edge 95 of the dispenser part 90. The component parts 91, 92can be joined by any one of the seams described in connection with theFIGS. 6-9. The dispenser part 90 is detachably joined to a reardispenser section 96, in order to form a dispenser housing 97. The reardispenser section 96 is arranged to be mounted on a vertical surface,such as a wall. In this example, the dispenser housing 97 is intendedfor a dispenser for a stack of paper towels or similar, which areremoved through a dispenser opening 98 in a lower surface of thedispenser.

FIG. 14 shows a second example of a dispenser comprising a dispenserpart according to the invention. In this example, a dispenser part 100is formed by a transparent first component part 101 and an opaque secondcomponent part 102. The first component part 101 and the secondcomponent part 102 are joined by a seam 103 extending from a first sideedge 104 to a second side edge 105 located along a lower delimitingsection of the dispenser part 100. The component parts 101, 102 can bejoined by any one of the seams described in connection with the FIGS.6-9. The dispenser part 100 is detachably joined to a rear dispensersection 106, in order to form a dispenser housing 107. The reardispenser section 106 is arranged to be mounted on a vertical surface,such as a wall. In this example, the dispenser housing 107 is intendedfor a dispenser for a roll of paper or similar, which is removed througha dispenser opening 108 in a lower surface of the dispenser.

FIG. 15 shows a third example of a dispenser comprising a dispenser partaccording to the invention. In this example, a dispenser part 110 isformed by a central transparent first component part 111 and an upperand a lower opaque second component part 112 a, 112 b. The firstcomponent part 111 and the second component parts 112 a, 112 b arejoined by seams 113 a and 113 b, respectively. Both seams 113 a, 113 bextend in parallel from a first side edge 114 to a second side edge 115of the dispenser part 110. The component parts 111, 112 a, 112 b can bejoined by any one of the seams described in connection with the FIGS.6-9. The dispenser part 110 is detachably joined to a rear dispensersection 116, in order to form a dispenser housing 117. The reardispenser section 116 is arranged to be mounted on a vertical surface,such as a wall. In this example, the dispenser housing 117 is intendedfor a dispenser for a stack of paper towels or similar, which areremoved through a dispenser opening 118 in a lower surface of thedispenser.

FIG. 16 shows a fourth example of a dispenser comprising a dispenserpart according to the invention. The figure shows a perspective, lowerview of a dispenser of the one-piece or single part type, in this case adispenser of a bracket type. According to the invention, the dispenserpart comprises a bracket 120 for containing or supporting a bag or boxof wipes B (indicated in dash-dotted lines). The bracket 120 comprises apair of transparent first component parts 121 a, 121 b on either side ofthe bracket 120 and a single rear and a lower opaque second componentpart 122. The first component parts 121 a, 121 b and the secondcomponent part 122 are joined by seams 123 a and 123 b, respectively.Both seams 123 a, 123 b extend from a first side edge 124 a, 124 b atthe rear of the bracket to a second side edge 125 a, 125 b adjacent thefront of the bracket 120. The component parts 121 a, 121 b, 122 can bejoined by any one of the seams described in connection with the FIGS.6-9. The bracket 120 is provided with a rear section 126 (not shown)allowing it to be attached to a wall or a similar vertical surface. Inthis example, the bracket 120 is intended for a dispenser for a box Bcontaining stack of paper towels or similar, which are removed through adispenser opening 128 in a lower surface of the dispenser.

A single part bracket dispenser can be made from at least two plasticcomponent parts, having two or more different colours or a combinationof transparent, frosted or opaque sections. A similar bracket typedispenser can be used for soap dispensers that comprise a one-piecebracket in or on which a soap re-fill bottle will be contained orsupported. In the latter case, the re-fill bottle can be made to looklike a “hood” or an outer cover as used in commonly available types ofsoap dispensers. In other words the refill (i.e. the soap bottle) willtake the place of one of the parts of the dispenser (i.e. the hood). Insuch cases the bracket type dispenser forms a single part dispenserdefined as a dispenser part according to the invention.

When selecting materials it must be determined that the resins used aregenerally compatible, with no antagonistic effects between resins.Suitable materials for use in the above method are acrylonitrilebutadiene styrene (ABS) plastics and/or methyl methacrylate-ABS (MABS)plastics. However, these materials are given by way of example only andthe invention is not limited to these materials. The materials tested inthe examples below are Terlux® TR2802 MABS (BASF Corp.) or Polylux® C2MABS (A. Schulman GmbH) for the transparent first part and Polyman® M/MIA40 ABS (A. Schulman GmbH) for the opaque second part.

A comparative bending test was performed using a selection of the abovematerials for the seams as described in connection with FIGS. 3 and4A-D. The test used conforms to ISO 178:2001. Test samples in the formof five individual strips with the dimensions 1 cm by 10 cm were cutfrom a number of injection moulded components. The seam configurationsincluded a prior art seam, shown in FIG. 3, as a reference sample, theseams shown in FIGS. 4A-D, and a sample comprising a length of ahomogenous opaque material having the same thickness as the referencesample. As indicated in Table 1, all but one of the samples comprising aseam was made by joining the same two materials. The samples were heldat each free end and subjected to a force applied to the seam. Duringthis test the peak load (MPa) and the stress at break (MPa) wasrecorded.

In Table 1, the samples 1A-1C represent a seam according to thereference seam of FIG. 3, where the samples comprise different materialsjoined at different injection temperatures. Similarly, samples 2A-2Brepresent a seam according to the seam of FIG. 4A, while samples 3-5represent the seams according to FIGS. 4B-D, respectively. Sample 6comprises a length of a homogenous opaque material with the samethickness as the reference sample.

In order to improve the properties of the seam between two componentparts it was also discovered that a purposeful selection of injectiontemperatures during the first and/or second injection moulding step hada positive effect.

According to one example, a dispenser part was made comprising Polylux®C2 MABS (A. Schulman GmbH) for the transparent first part and Polyman®M/MI A40 ABS (A. Schulman GmbH) for the opaque second part of thedispenser part. The injection, or barrel, temperature was modified forthe first injection moulding step. According to a materials cataloguecomprising technical data for the said plastic materials supplied by A.Schulman GmbH; “Schulamid”®; page 28; (3^(rd) edition May 2006), it canbe seen that the recommended injection temperature for Polylux® C2 MABSis 200-240° C.

When performing the two-component injection moulding process accordingto the invention, the first injection moulding step used an injectiontemperature of 260-290°, preferably 280° C., for the transparent firstcomponent part. Combined with the seam configuration as shown in FIGS.4A-D, in particular FIG. 4A, subsequent testing showed that theincreased injection temperature during the first injection step resultedin an improved structural strength of the seam joining the componentparts.

TABLE 1 Bending test Stress at Temperature (° C.) Peak Load Break No.Material Opaque/Transparent (MPa) (MPa) 1A Polyman/Terlux 240/240 34.839.8 1B Polyman/Polylux C2 240/240 24.0 29.6 1C Polyman/Polylux C2240/280 28.3 33.9 2A Polyman/Polylux C2 240/240 58.2 64.8 2BPolyman/Polylux C2 240/280 64.4 71.8 3 Polyman/Polylux C2 240/280 39.729.8 4 Polyman/Polylux C2 240/280 44.4 33.8 5 Polyman/Polylux C2 240/28030.7 19.5 6 Polyman 240 60.9 4.8 7 Polylux C2 280 53.6 4.7

As can be seen from Table 1, samples 2A and 2B representing the seamshown in FIG. 4A will provide an adhesion between the two componentparts that is equal to or better than sample 6, comprising a length of ahomogenous opaque material. The test also shows that the strength of theseam in samples 2A and 2B is almost twice that of the reference sample,irrespective of material or injection temperature.

During the tests it was discovered that samples 3-5, in spite of havinga seam of substantially the same configuration, tended to break adjacentthe rounded end section of the transparent component parts where itjoined the opaque component part. It would appear that the end sectioncreated a weakened section at this point. In spite of this, the strengthof the samples 3-5 is still equal to or higher than that of thereference samples 1A-1C.

An additional test performed was an impact test, simulating an externalforce applied to a dispenser part shaped as a front cover in the regionof the seam. A suitable test developed for this purpose involvessuspending a weight attached to a pivoted arm, which weight is releasedto strike a limited area of a front surface of a dispenser cover mountedon a fixed surface or to a support for attaching the dispenser to awall. This test simulates a dispenser being struck with a predeterminedforce by an object or a person.

According to one example, the test used a 13 kg weight attached to anarm having a length of 0.75 m. The part of the weight arranged to impacta front surface of the dispenser part had an area corresponding to theaverage area of an adult male human fist, corresponding to a flatrectangular area of about 63 cm² (7×9 cm). The arm to which the weightis attached was pivoted from a vertical to a horizontal position,through an arc of approximately 34°, and released. This angle can beselected and set to give a repeatable desired impact energy. The impactenergy absorbed by the dispenser part using the test settings describedabove is intended to correspond to a value of 15 Joule (J). Duringtesting, dispenser parts were subjected to impacts of 10 and 15 J,respectively. The lower value was selected as a minimum acceptable leveland the higher value was selected as a preferable level for impactstrength without cracking.

A number of material combinations were tested and rejected due to atleast one of the component parts being shattered by the impact. Furthermaterial combinations were tested and rejected due to cracking orsplitting of the seam between the component parts.

After performing a significant number of tests to determine the strengthof various seam configurations and material combinations it wasdetermined that a combination of ABS materials or ABS and MABS materialsresulted in a seam that had the desired properties. In addition tosuitable surface finish properties, relating to e.g. gloss and scratchresistance, an injection moulded dispenser part comprising a seamaccording to the invention was found to have the desired strength and towithstand the impact test without cracking. Examples of such materialsare Polylux® C2 MABS (A. Schulman GmbH) for the transparent first partand Polyman® M/MI A40 ABS (A. Schulman GmbH) for the opaque second partof the dispenser part.

The tool design used in the described example is a rotating plate. Thiscomprises a two-station tool that rotates in a vertical (or horizontal)direction. The rotating plate is held in a first position at a firstinjection station for the injection of the first material. It is thenrotated into a second position at a second injection station for theinjection of the second material.

An alternative tool design is a core back. In a core back, a slidingcore is first closed and the first material is injected. The slidingcore is then opened and the second material is injected.

The invention is not limited to the above examples, but may be variedfreely within the scope of the appended claims. For instance, in theabove examples a combination of transparent and opaque materials aredescribed. In addition, combinations of one or more coloured and/ortransparent materials may be used. Also, the examples describe a singleseam extending horizontally or at an angle across the front surface ofthe dispenser part. Alternative solutions may comprise one or more seamsarranged vertically or to enclose a single corner. The seam need notonly be located along a straight line, as described above, but can alsobe given a curved, wavy or an irregularly shaped line.

The invention claimed is:
 1. Method of manufacturing a dispenser part,comprising: performing a first injection moulding step in a mould toproduce a first component part having a first edge and comprising, in atransverse direction to the first edge, a first inner step adjacent aninner surface of the dispenser part, a first outer step adjacent anouter surface of the dispenser part, and a first intermediate stepbetween the first inner step and the first outer step, the first outerstep having a height in the transverse direction that is larger than aheight of the first intermediate step in the transverse direction;retaining the first component part in the mould; and performing a secondinjection moulding step in said mould to produce a second component parthaving a second edge and to join the second edge of the second componentpart to the first edge of the first component part to form a seam, suchthat the second component part is flush with each of the steps of thefirst component part.
 2. The method according to claim 1, wherein theheight of the first intermediate step is 0.05 to 3 mm.
 3. The methodaccording to claim 1, wherein the first inner step, the first outerstep, and the first intermediate step are formed along the first edgefrom a first free side edge on a first side surface of the dispenserpart to a second free side edge on a second side surface of thedispenser part.
 4. The method according to claim 1, further comprisingmoulding each of the first inner step, the first outer step, and thefirst intermediate step to form a first contact surface at right anglesto the outer or the inner surface of the dispenser part, and a secondcontact surface extending at an angle to the first contact surface. 5.The method according to claim 4, further comprising moulding the secondcontact surface to form raised contact increasing means along the lengthof the seam.
 6. The method according to claim 5, further comprisingmelting the raised contact increasing means during the second injectionmoulding step.
 7. The method according to claim 4, further comprisingmoulding at least one of the first inner step, the first outer step, orthe first intermediate step to form a third contact surface at rightangles to the outer or the inner surface of the dispenser part.
 8. Themethod according to claim 1, wherein the height of each intermediatestep is 0.05 to 2 mm.
 9. The method according to claim 1, wherein theseam includes at least two intermediate steps and wherein the heights ofthe at least two intermediate steps are equal.
 10. The method accordingto claim 1, wherein the steps are formed so that a thickness of thefirst edge is reduced with each step towards the inner surface of thefirst component part, the thickness of the first edge extending betweenthe outer and the inner surface of the dispenser part.
 11. The methodaccording to claim 5, further comprising moulding the raised contactincreasing means to form at least one projection along the length of theseam.
 12. The method according to claim 11, further comprising formingat least one flat projection extending at right angles to the secondcontact surface along the length of the seam.
 13. The method accordingto claim 11, wherein multiple, individual projections are formed alongthe length of the seam.
 14. The method according to claim 5, furthercomprising moulding the raised contact increasing means to form at leastone ridge along the length of the seam.
 15. The method according toclaim 14, wherein the at least one ridge has a V-shaped cross-section.16. The method according to claim 14, wherein multiple, parallel ridgeshaving a V-shaped cross-section are formed.
 17. The method according toclaim 11, further comprising forming at least one projection or ridgehaving a height up to half the height of the first outer step or thefirst inner step.
 18. The method according to claim 11, whereinprojections having the same or different heights are formed.
 19. Themethod according to claim 1, wherein the first component part is mouldedfrom a transparent material.
 20. The method according to claim 1,wherein the second component part is moulded from an opaque material.21. The method according to claim 1, further comprising injecting atleast one of the materials for the first or second component parts at atemperature higher than a standard injection temperature for thematerial used.
 22. The method according to claim 1, further comprisinginjecting at least one of the materials for the first or secondcomponent parts at a temperature selected above a recommended injectiontemperature for the particular material.